Trans oil cooler...return line?
Thread Starter
Racer
Joined: Sep 2006
Posts: 469
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From: Sandy TX
Trans oil cooler...return line?
Which line coming from the radiator cooler is considered the trans oil "return" line? Upper or lower?
I'm installing an aftermarket trans cooler and need to tap in to the return line according to the instructions. Also...does it really matter? The cooler will still cool even if you tap into the supply line, no?
I'm installing an aftermarket trans cooler and need to tap in to the return line according to the instructions. Also...does it really matter? The cooler will still cool even if you tap into the supply line, no?
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
yes it does matter.....you want to cool the trans fluid and then heat it to water temp as opposed to cooling it to water temp and then cooling it even more.....cold transmissions shift funny
edit: although that is contrary to what your instructions say???? you may want to get some more opinions on this one..how are you going to use the car? strip or street?
edit: although that is contrary to what your instructions say???? you may want to get some more opinions on this one..how are you going to use the car? strip or street?
Last edited by bobs77vet; Apr 3, 2007 at 12:16 AM.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
I have looked all over the place and have yet to find ANYTHING on a minumum operating temp on a transmission. The ONLY thing I have found is keep it under 200, the cooler the better. I would skip the radiator and just go with an external cooler. My personal choice is a dual pass extruded aluminum heat sink type. No moving parts, installed in the slipstream under the car
Thread Starter
Racer
Joined: Sep 2006
Posts: 469
Likes: 0
From: Sandy TX
The car had an external cooler (only) and, in very hot weather (after extended freeway driving), the tranny would "slam" between 1st & 2nd. I assumed this was because the external cooler was too small (it looked tiny...3/8" thick x 6" x 8"). If I turned the car off for a few minutes and re-started all was well (until the next extended run).
So, I installed a new radiator with new lines and hooked them up as per "factory" thru the rad cooling ports. Same problem.
Now, I've got a nice big auxillary cooler to install. I figure if I install this in-line with the rad and it solves the problem, all is good. If the tranny still overheats/slams, then I know I have bigger problems. I'm thinking it is cheaper to try adding a cooler than to automatically assume the tranny is toast and have it rebuilt.
So, I installed a new radiator with new lines and hooked them up as per "factory" thru the rad cooling ports. Same problem.
Now, I've got a nice big auxillary cooler to install. I figure if I install this in-line with the rad and it solves the problem, all is good. If the tranny still overheats/slams, then I know I have bigger problems. I'm thinking it is cheaper to try adding a cooler than to automatically assume the tranny is toast and have it rebuilt.
Last edited by Topless75; Apr 3, 2007 at 12:54 AM.
Race Director
Joined: Sep 2004
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
no i don't know, but here is some logic.....the top line is the supply line that uses pressure to pump the trans fluid through the radiator top inlet and out of the bottom radiator inlet back to the trans and this also use gravitiy to help the flow
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So...we have one vote for TOP and one vote for BOTTOM...
Racer
Joined: Jan 2007
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From: Pittsfield, Ohio
Sorry. I dont know either.
Drifting
Joined: Sep 2006
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From: MS
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
from the book......"at the transmision the feed line -transmission to cooler is always the lower line and the return line- cooler to transmission is the upper"....wfo76 wins!
Le Mans Master
Joined: Dec 2006
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I asked my transmission guy about this today. Bob is absolutely correct.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
I have looked all over the place and have yet to find ANYTHING on a minumum operating temp on a transmission. The ONLY thing I have found is keep it under 200, the cooler the better. I would skip the radiator and just go with an external cooler. My personal choice is a dual pass extruded aluminum heat sink type. No moving parts, installed in the slipstream under the car
Apparantly lack of quick heating of the fluid is good business in cold climate areas.
Thread Starter
Racer
Joined: Sep 2006
Posts: 469
Likes: 0
From: Sandy TX
I asked my transmission guy about this today. Bob is absolutely correct.
From the web:
It is normally preferable to have the external cooler plumbed in series with the return line. This provides the most efficient cooling by about 5%. However, the port at the top of the radiator where the return line exits is kind of a tight squeeze to work with, so you can tap into it at the transmission but this requires running longer fluid lines back to the radiator area (some of us have done this with no problems).
Alternatively, plumb into the supply line. It has slightly less cooling efficiency but simplifies the installation a little bit (no picture available).
Last edited by Topless75; Apr 3, 2007 at 10:23 PM.
Thread Starter
Racer
Joined: Sep 2006
Posts: 469
Likes: 0
From: Sandy TX
Sorry Danny. I checked on this today. In warmer climates such as Kalifornia and Florida, it is not critical. The hydraulic pumping action will bring it up to temp rather quickly. In colder climates, the fluid will thicken and mess up the tranny quickly due to poor circulation/thick viscosity. I get this from my Tranny guy of 35 years, and he reads all the trade rags.
Apparantly lack of quick heating of the fluid is good business in cold climate areas.
Apparantly lack of quick heating of the fluid is good business in cold climate areas.
That's what I've read. There is a temp-controlled bypass valve (thermostat) that recirculates the tranny fluid bypassing the external cooler until it reaches operating temp. They recommend installing these in Northern climates.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
Not so sure. That tranny can get pretty hot without any help. I touched the external cooler after running the engine for less than a minute. It was already hot.
From the web:
It is normally preferable to have the external cooler plumbed in series with the return line. This provides the most efficient cooling by about 5%. However, the port at the top of the radiator where the return line exits is kind of a tight squeeze to work with, so you can tap into it at the transmission but this requires running longer fluid lines back to the radiator area (some of us have done this with no problems).
Alternatively, plumb into the supply line. It has slightly less cooling efficiency but simplifies the installation a little bit (no picture available).
From the web:
It is normally preferable to have the external cooler plumbed in series with the return line. This provides the most efficient cooling by about 5%. However, the port at the top of the radiator where the return line exits is kind of a tight squeeze to work with, so you can tap into it at the transmission but this requires running longer fluid lines back to the radiator area (some of us have done this with no problems).
Alternatively, plumb into the supply line. It has slightly less cooling efficiency but simplifies the installation a little bit (no picture available).
Since we are referencing the web, check out the install instructions at Bowtie Overdrives, They will only warranty their transmissions when the radiator and aftermarket cooler is installed in a specific order.
Thread Starter
Racer
Joined: Sep 2006
Posts: 469
Likes: 0
From: Sandy TX
Found it...they require an auxilliary cooler in-line with the return line. They want the tranny temp 30 ~ 50 degrees cooler than the rad temp.
Last edited by Topless75; Apr 3, 2007 at 11:00 PM.
